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  1. #1

    Post My Yamaha 1100 Triple Mikuni 38 Carb Rebuild Thread

    I'm in the middle of rebuilding my carbs right now, so this thread is going to cover some things I've learned so far and some questions I have as I go... I'm updating this post as a "summary" of answers people have helped with and things I've figured out as I go, but for details you can read the whole thread.

    What I've learned so far:

    1) Contrary to what some manuals may tell you, it's much easier to remove the carbs if you go ahead and remove the lower portion of the flame arrestor. Stuff a few rags in the flame arrestor while you're pulling the bolts holding it to the carbs as a "CYA" measure.

    2) If you remove the flame arrestor, it's not a bad idea to have a new gasket to go between the flame arrestor and the carbs handy. It's a less than $5 part and it doesn't come with your rebuild kits.

    3) A "stubby" 12mm wrench is a must to pull the carbs from the manifold.

    4) VICE GRIPS... big beefy vice grips... use them to break the screws loose to get inside the carb. Clamp them down parallel to the head of the screw to get as many teeth on the head of the screw as you can. Once you break the screws loose, you can use a screwdriver for the rest. (thanks to addicted for this one)

    5) When you get to the point of taking the regulator blocks out, there are two phillips screws. Be sure you use the right size driver as these things strip EASILY. After I stripped mine, I read my manual and it specifically says that before turning, tap the driver in with a hammer in order to make sure it has a good grip.

    6) If it's too late for step #5 (as it was for me) use a hand impact wrench and a hammer to get the stripped screws out. (thanks to jdog800)

    7) Instead of buying/building a pop-off tester, use an air compressor with a regulator and a blow gun attachment with a rubber nozzle. Dial the regulator in to wherever you want to start testing, hold the rubber nozzle in the hole where you removed the filter, and pull the trigger. If it doesn't pop-off, increase the PSI and test again. If the rubber nozzle doesn't create a good seal around the filter hole: #1, you'll hear it, and #2, you probably won't get a pop, so readjust and try again.

    My questions:

    To start with, the outside of my carbs are in pretty crappy shape - I think from 12 years gas, oil, water and heat. The paint is peeling off from everywhere, there is some corrosion where the gas lines attach, and they're just generally dirty. That being said, everything on the inside looks like it's in great shape.

    1) I've read you can wash the bodies in soapy water with a brush. Can I just dump all three in a bucket of soapy water and brush them off? I'm a little bit concerned with some of the paint or other particles getting into places it shouldn't be if I try this.

    Thanks for any input...
    Last edited by kingstretch; 08-11-2008 at 07:29 AM.

  2. #2
    cheatin' piston popper addicted's Avatar
    Join Date
    Jul 2006
    north jersey
    heat the carb bodies with a heat gun or torch. then get out the vice grips. the screws should coume out that way. It's corrosion between the aluminum carbs and ferrous screws.

    You can clean the carbs with anything really. As long as you are replacing all the seals you should be ok. just make sure you blow out all the passages with carb cleaner and then comp. air.

  3. #3
    watch the torch around the fuel vapors if u go that route
    those carbs tend to hold a lot of fuel

  4. #4
    cheatin' piston popper addicted's Avatar
    Join Date
    Jul 2006
    north jersey

  5. #5
    I think the only thing I have available is a torch... I've got a small butane powered soldering iron with a torch attachment I might be able to use assuming it will get hot enough. But just to clarify...

    1) use the torch to heat up the area around the screw.
    2) grab outside edges of screw head with vice grips and twist to remove screws.

    What am I risking with the fuel vapors? Obviously that's not anything I can "see", I imagine I would just need to keep the torch away from where the fuel lines connect to avoid any chance of ignition. Let's say I mess up and it DOES ignite, are we talking a quick burn off or a minor explosion (shouldn't be pressurized, so I wouldn't think it would explode).

  6. #6
    cheatin' piston popper addicted's Avatar
    Join Date
    Jul 2006
    north jersey
    to be safe, blow out the fuel with compressed air. Cap the return nipple, blow through the in nipple. most of the fuel will come out the jets. Do all this with caution. if you are uncertain try a hair dryer or maybe a soldering iron to heat the aluminum. the goal is that aluminum expands roughly 7x more than steel. heat the aluminum and it will expand, hopefully enough to get the screws out. Maybe try soaking the screws with pb blaster overnite first?

    Just remember that common sense is your best friend. if you think you might blow yourself or your house up, try something else first.

  7. #7
    What PSI should I try and put into the carbs to blow them out? I would imagine it would only take a couple of PSI just to pump the remainder of the fuel out.

    I could try the soldering iron route, but I have the butane iron which has an exposed flame anyway. I'd probably run about the same level of risk. Could I just cap off all of the nipples which would (I assume?) eliminate the source for the vapors?

  8. #8
    ....back from the dead.... J-ME's Avatar
    Join Date
    Aug 2005
    Dunk the carbs repeatly in a bucket of water to try and inert the fuel.

    Make sure you have some quality vice grips that aren't wobbly at the rivets.

    Let us know how it goes. I do like 2-3 sets of carbs a week. Some get very ugly when it comes to salt water.

  9. #9
    Quick thanks to everybody for the suggestions...

    Tonight I got all the covers off, pulled the diaphragms, pulled the filters, pulled most of the gaskets and o-rings, pulled two of the regulator blocks. Here's where I'm stuck...

    My first regulator block didn't go very well - I think I didn't have the right driver on it and the screws stripped almost immediately. As soon as I caught it I switched up drivers, but it's too late for the first regulator block. The only feasible solution I've been able to find for this is to use a screw extractor (drill down the shaft of the screw, insert the extractor, and pull it). I would need to buy the EXACT screws again though - and who knows if I'll be able to find them. Does anybody have any other good ideas for this??

    Issue #2: I went ahead and continued work on the other two carbs. I went to do a pop off test BEFORE replacing parts in order to get a baseline that I could compare to when I was rebuilding. The "how-to" I looked at for the pop-off tester was apparently for a different model carb. The last part before the carb is just a length of 1/4" fuel line which plugs into the carb. This doesn't work for where I need to plug the pop off tester into my carb. I'm missing some sort of plastic fitting with an o-ring on it that I've seen in a few pictures since then. What is this thing and where would I go about finding it?

    Thanks again - this doesn't seem like it would be that hard if all of the screws weren't working against me...

    Also - I'm updating my first post as I go along...

  10. #10
    I did some more reading on pop-off testers... it looks like I'm supposed to hook the 1/4" line from the pop-off tester to the fuel inlet and block up the fuel return(s)... If that's the case, I'm not entirely sure why the guide I was reading showed it working a little bit differently. I guess maybe there's more than one way to skin the cat. Now I just need to figure out what my pop-off pressure is SUPPOSED to be...

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